Technical Field
This disclosure relates generally to orthopedic implants and, more particularly, to orthopedic implants adapted for fracture repair and methods for repairing fractures.
Description of the Related Art
A variety of systems and devices are conventionally used to treat bone fractures in humans or animals. Bone fractures typically heal naturally as a result of normal growth or regeneration processes. Treatment of bone fractures generally includes placing bone fragments into an anatomically correct position and orientation, referred to as “reduction,” and maintaining the fragments in place until healing naturally occurs, referred to as “fixation.” Accordingly, a primary objective in the treatment of bone fractures is the fixation or stabilization of the reduced, fractured bone for the duration of the healing process.
Conventional systems and devices for treatment of fractures include external fixation means, such as traction, splints, or casts, and internal fixation means, such as plates, nails, pegs, screws, and other fixtures. Internal fixation devices are installed on or in the fractured bone across the fracture site. For example, plates, screws, pegs apply compression forces across a fracture site, thereby aiding in stabilizing a bone fracture across the fracture site. Intramedullary nails are installed longitudinally into the intramedullary (IM) canal of a fractured bone across the fracture site and provide torsional stabilization as well as load sharing along the central axis of the bone.
One common problem with internal fixation devices is that the installation of such devices is generally dependent on the presence of sufficient amounts of high quality bone tissue in the vicinity of the fracture. When bone tissue is lost, due to disease, a pathological condition or for other reasons, it may be difficult to install internal fixation devices to stabilize the bone sufficiently for healing. For example, persons with thin or fragile bones, such as osteoporosis patients, avascular necrosis patients and patients with metastatic bones, may be particularly prone to difficulties with fixation and healing of fractures. Unfortunately, these are the very patients that are most prone to bone fractures. While external fixation devices and methods are available, external fixation devices can be cumbersome, uncomfortable, limit or prevent ambulation and therefore generally fail to satisfy the needs of such patients.
Current fixation devices, both internal and external, also fail to meet the needs of injured soldiers and other trauma victims. Specifically, approximately thirty percent of all battlefield trauma cases involve bone fractures, typically due to high energy events, such as blasts or gunshots. For example, the combination of comminuted open fractures with large bone loss and significant soft tissue loss are common battlefield traumas. Such cases, often referred to as “segmental defects,” are very difficult to treat and typically require multiple surgeries and long healing/rehabilitation times that can last as long as two years. Amputations in these cases are common.
Current treatment techniques include the use of internal and external fixation with titanium plates, screws, and rods or IM nails, and the Ilizarov distraction method for bone-lengthening. However, current techniques suffer from significant deficiencies, some of which arise from the mechanical property mismatch between titanium and bone. This mismatch leads to complications including further fractures, delayed healing, and a high prevalence of infection. Furthermore, currently available techniques do not provide the most effective treatment in repairing large segmental defects, which are generally defined as a defect or missing bone segment that exceeds 2 cm in length or width. Because many currently available fixation devices are not fully load-bearing, the soldier or patient may be effectively incapacitated during the recovery period.
Therefore, in light of the above problems, more effective fixation methods and devices are urgently needed for the treatment of both common bone fractures as well as bone fractures considered to be large segmental defects.